ABSTRACT
During the past 15 years increasing attention has been given to roles of protists 2 to 200 µm in size in aquatic ecosystems. Application of epifluorescence staining methodologies overcame this deficiency and has been the basis for much of the new information about aquatic protists. Loss of naked flagellate and ciliate cells due to sample handling: Passing a sample through any kind of screen inevitably results in lysis of some protists, particularly larger naked ciliates. Anecdotal information suggests that the abundance of most microbial cells, including bacteria and protists, decreases with time in preserved liquid samples. Various workers have used 1 to 5% final volume formalin (37% formaldehyde) to preserve protists in water samples. Until recently, it has been common practice to store aldehyde-preserved samples in the dark and cold (5°C) for days to 1 to 2 weeks, or Lugol-preserved samples in the dark at room temperature for weeks to months, prior to inspection.
